Various instruments are used for removing foreign objects from the body of a patient. For example, such instruments may be used for removal of stones such as kidney stones, gallstones, and the like from various sites along the urinary tract of a patient's body. Retrieval devices are also widely used for removing foreign articles from the vascular system of a patient. In such cases, examples of the foreign articles include vascular stents, vena cava filters, and parts of medical devices such as catheters, guide wires, cardiac leads, or the like, which may break and become detached during medical procedures or need removal for other reasons.
Some types of these instruments employ a collapsible wire basket arranged within a flexible catheter formed as a tubular sheath adapted to penetrate body passages to reach the location where the object is to be evacuated. Another known type of retrieval device for use within a body vessel is a “snare” configured as one or more distal loops which, in operation, may be positioned over a free end of the foreign body, and which may be collapsed and tightened around the foreign body so that it may be retrieved.